Image reading apparatus and image forming apparatus

ABSTRACT

An image reading apparatus includes an original resting glass sheet for resting allowing an original thereon, a support device for supporting an end portion of the original resting glass sheet, and a movable image reading unit for reading image information of the original, wherein the support device is provided with a cutout for preventing the support device from coming into contact with the image reading unit when the image reading unit moves outwardly beyond the end portion of the original resting glass sheet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus for readingimage information of originals, for example, an image reading apparatus,such as an image scanner or a facsimile apparatus. The present inventionalso relates to an image forming apparatus, such as a copying machine,in which the image reading apparatus is mounted.

2. Related Background Art

Conventionally, as copying machines, composite machines having a copyingfunction and a facsimile function, and image scanners having an autodocument feeder (hereinafter referred to as ADF), there have beenproposed a number of apparatuses having both the function by whichscanning is performed with the original remaining stationary on a glasssheet surface and the function (flow reading function) by which scanningis performed while moving the original with the optical system beingstationary.

Regarding the construction of the portion in which the flow reading oforiginals is performed, various proposals have been made in connectionwith the ensuring of the reading position, the conveying of originals,etc.

For example, Japanese Patent Publication (Kokoku) No. 3-37348 proposes aconstruction in which an ADF is secured to the apparatus main body, withthe ADF being separated from an original pressure plate, and in whichthe height of the reading position using the original glass stand ismade the same as the height of the position at which the original fed bythe ADF is read.

Further, Japanese Utility Model Publication (Kokoku) No. 5-43561discloses a construction in which there is provided a presser member fordefining a fixed gap between a contact-type image sensor (hereinafterreferred to as CIS) and an original pressure roller opposed thereto toensure a focal distance.

Further, Japanese Patent Application Laid-Open (Kokai) No. 63-138863discloses a construction in which a U-turn-conveyed original is read,and then conveyed in a discharge direction by way of a jump member by aguide member biased toward a glass sheet surface.

Japanese Patent Application Laid-Open (Kokai) No. 61-139920 proposes anapparatus in which, to maintain a fixed distance between a stationaryoriginal glass stand and an optical system moving in a sub-scanningdirection, a roller protrudes from the optical system toward the backsurface of the original glass stand and a biasing effect is provided,thereby maintaining a fixed focal distance in conformity with theconfiguration of the original glass stand.

Japanese Patent Application Laid-Open (Kokai) No. 10-186535 discloses anapparatus in which, as shown in FIG. 8, a stationary original D on afirst glass sheet 12 is read while moving a CIS 1 as image reading meansin the sub-scanning direction and in which, on a second glass sheet 13,the CIS 1 remains stationary and reads a moving original S.

In the above-mentioned invention, however, when the maximum-sizeoriginal D is read on the first glass sheet 12, the CIS 1, after leavingthe trailing end E of the original, undergoes speed reduction andadvances by a distance F of approximately 10 mm before it stops.

In the above-mentioned conventional techniques, the sheet scannerportion which reads the original S while moving the original and theflat bed scanner portion which reads the original D arranged on theoriginal glass stand, are respectively secured to the main body, sothat, to form an image reading apparatus using a contact-type imagesensor (CIS) of a shallow focal depth, the following problems areinvolved.

In the construction proposed in Japanese Patent Publication No. 3-37348,the optical system is scanned in accordance with the structure of themain body, and the glass sheet of the sheet scanner portion and theglass sheet of the flat bed scanner portion are separated andrespectively fixed in position.

Thus, in an apparatus utilizing a CIS, it is necessary to set theheights of the two glass sheets with high accuracy to guide the originalwithin the focal depth of the CIS. Furthermore, taking into account theconstruction from the sensor to the glass sheets and the number ofparts, it is difficult to ensure an accuracy which meets a desiredlevel. To ensure such accuracy, it is necessary to perform heightadjustment on the glass sheets or the optical system in the assemblystep.

Further, since the ADF portion is secured to the apparatus main body ina state in which the ADF portion is separated from the pressure plate,the original supply portion is arranged outside the pressure plate, sothat the size of the entire main body is rather large as compared withan apparatus in which the original supply portion is provided on thepressure plate.

In the case of the proposal made in Japanese Patent ApplicationLaid-Open No. 63-138863, there is provided a jump stand 4 (FIG. 8) forpicking up an original that has undergone a U-turn and has been read.When the glass sheet on the sheet scanner side and the glass sheet onthe flat bed scanner side are integrated, it is necessary, in order topick up the original by the jump stand 4, to arrange the side of thejump stand 4 which first comes into contact with the original (theupstream side with respect to the original conveying direction) lowerthan the glass sheet surface. Otherwise, original jamming will be causedby the edge of the jump stand 4.

On the other hand, when the upstream side of the jump stand 4 isarranged lower than the glass sheet surface, it is necessary to providea groove in the glass sheet surface.

Provision of a groove in the glass sheet leads to a substantial increasein cost. Further, it also involves an extreme deterioration in thestrength of the portion where the groove is provided.

Unlike the apparatus as disclosed in Japanese Patent ApplicationLaid-Open No. 63-138863, in which the glass sheet of the sheet scannerportion and the glass sheet of the flat bed scanner portion areintegrated, a construction in which the glasses are separated as in thecase of the proposal made in Japanese Patent Application Laid-Open No.61-49920 has a problem in that the focal distance is small and, in anapparatus using a CIS in which the distance to the back surface of theglass sheet is approximately 1 mm, the glass sheet support portion and astep portion between the glass sheets are in the way, making itdifficult to move the CIS between the sheet scanner portion and the flatbed scanner portion.

In the case of the proposal made in the Japanese Patent ApplicationLaid-Open No. 10-186535, the CIS 1 moves while making a verticalmovement between the first glass sheet 12 and the second glass sheet 13,and the problem of the movement between the two glass sheets is solvedup to a point. However, it is necessary to cause the CIS to move by agreat distance in the sub-scanning direction.

FIG. 8 shows a second embodiment of the above-mentioned conventionaltechnique, in which the support portion between the glass sheets 12 and13 is formed by a step of 0.5 mm having a slope, and the CIS 1 held incontact with the glass sheets by a roller is moved. In the case of aglass sheet of a large size, such as an A-3 size, a problem in terms ofstrength is involved when supporting the glass sheet with a step of 0.5mm.

FIG. 9 shows a third embodiment of Japanese Patent Application Laid-OpenNo. 10-186535, in which the support portion between the glass sheets 12,13 is flush with the glass sheet surfaces only in the portion in whichthe CIS 1 moves while being in contact with the glass sheets 12, 13. Inthis construction, the glass sheet edge portion may collide with thecontact member 2 of the CIS 1, in which case the contact member 2 isworn, resulting in a change in the focal distance of the CIS 1.

Apart from this, although not explicitly proposed as an invention, inthe conventional construction of FIG. 8 there is provided a speedreduction range F of approximately 10 mm to the right of the right-handend E of the original D, and, further on the outside thereof, thereexists an extra portion G of approximately 7 mm at which the frame 3supports the end portion of the first glass sheet 12.

Further, to the left of the second glass sheet 13, there exists aportion H (having a length of approximately 5 mm) supported by the frame3, with the result that the apparatus is rather long.

In the apparatus shown in FIG. 9, in which the distance between thefirst glass sheet 12 and the second glass sheet 13 is large, there isthe possibility of the CIS 1 being thrust into the gap therebetween inan inclined state.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a high-performanceimage reading apparatus and image forming apparatus in which a reductionin apparatus size is possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an image reading apparatus according to anembodiment of the present invention;

FIG. 2 is a front sectional view of the image reading apparatus of theembodiment of FIG. 1;

FIG. 3 is a right-hand side sectional view of the image readingapparatus of the embodiment of FIG. 1;

FIG. 4 is a perspective view showing a copying machine in which an imagereading apparatus according to the embodiment of FIG. 1 is mounted;

FIG. 5 is a left-hand side sectional view of the copying machine inwhich the image reading apparatus of the embodiment of FIG. 1 ismounted;

FIG. 6 is a right-hand side sectional view of the copying machine inwhich the image reading apparatus of the embodiment of FIG. 1 ismounted;

FIG. 7 is a front sectional view showing an image reading apparatusaccording to another embodiment of the present invention;

FIG. 8 is a front sectional view showing a conventional image readingapparatus; and

FIG. 9 is an enlarged view showing a conventional image readingapparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will now be described in detailwith reference to the drawings. The sizes, materials, configurations,positional relationship, etc. of the components given in the followingdescription should not be construed restrictively unless particularlyspecified.

An embodiment of the present invention will be described with referenceto FIGS. 1 through 7. FIG. 1 is a perspective view of a planar scanningdevice (hereinafter referred to as “flat bed scanner”) according to anembodiment of the present invention in which an optical system unit(image reading unit) is mounted, FIG. 2 is a front sectional view of theflat bed scanner, FIG. 3 is a right-hand sectional view of the flat bedscanner, and FIGS. 4 through 6 are diagrams showing an image formingapparatus in which the flat bed scanner is mounted.

In FIGS. 1 through 3, numeral 1 indicates a contact-type image sensor(hereinafter referred to as CIS) serving as an image reading means, inwhich a long-focus SELFOC lens (trademark) (not shown) is provided. Itis set so as to focus on an original glass stand 12 having a thicknessof 4 mm and serving as a first light transmitting member.

Further, in the CIS 1, there is provided a cold cathode tube (Xe-tube)(not shown), making it possible to perform a long-focus, high-speedscanning of up to approximately 0.4 msec/line in the main scanningdirection. The cold cathode tube is controlled by an inverter circuit 22provided outside the CIS 1.

Numeral 12 indicates the original glass stand, which serves as theoriginal resting means. A pair of height regulating portions 2 serve asregulating means and are formed of a material providing slidability. Theheight regulating portions 2 are arranged at both ends of the uppersurface of the CIS 1, at positions outside the main-scanning region,which is of the width of an image readable region extending in the mainscanning direction that is perpendicular to the direction in which theCIS 1 moves. The height regulating portions 2 are in contact with theback surface of the original glass stand 12 to determine the focaldistance of the CIS 1.

The height regulating portions 2 are provided at outside positions withrespect to the main scanning direction of the reading line 1 b, and arearranged in front of the width end of the original glass stand 12 and aflow reading glass sheet 13 serving as a second light transmittingmember.

This arrangement is adopted in order to prevent the read image frombeing adversely affected even if the portions of the lower surface ofthe original glass stand 12 which are in contact with the tops of theheight regulating members 2 are worn to generate contact marks when theheight regulating portions 2 move while in contact with the lowersurface of the original glass stand 12.

A material providing slidability is selected for the height regulatingmembers 2. In particular, it is desirable to adopt a polyacetal-based orteflon-based material, which provides a self-sliding effect.

The length of the height regulating members 2 as measured in thesub-scanning direction, in which the CIS 1 moves, is larger than doublethe distance between the original glass stand 12 and the flow readingglass sheet 13.

Due to this arrangement, if the image reading unit having the regulatingmeans and the CIS 1 passes the gap between the original glass stand 12and the flow reading glass sheet 13, it is possible to prevent amalfunction, for example, of the CIS 1 being caught by a step or thelike generated between the original glass stand 12 and the flow readingglass sheet 13.

The CIS 1 is elastically supported by springs 6, which are secured to acarriage 5, so as to be upwardly biased, and held in close contact withthe back surface of the original glass stand 12. Due to thisconstruction, it is possible to eliminate factors leading to a verticalvariation in the position of the CIS 1, such as the height of a guideshaft 7 and the height of a bent portion 3 a of the frame 3, and toclear away the influence of a deviation in the focal distance. As aresult, it is possible to design the parts with an accuracy of a generaltolerance level, thereby preventing an increase in cost.

The carriage 5 is supported through a bearing 5 b by the guide shaft 7so as to be slidable with respect to the guide shaft 7. The end portionsof the guide shaft 7 are secured to the frame 3 so as to horizontallysupport the guide shaft 7, and the frame 3 is provided with bentportions 3 a, 3 b extending parallel to the guide shaft 7. Slidingmembers 5 c are brought into contact with the bent portions 3 a, 3 b,whereby the carriage 5 is roughly maintained in its horizontal position.When the carriage 5 moves in the sub-scanning direction along the guideshaft 7, the sliding members 5 c move on the bent portions 3 a and 3 bwhile in contact therewith.

Numeral 10 indicates a timing belt for moving the carriage 5 in thesub-scanning direction, and numeral 11 indicates a stepping motor.

Referring to FIG. 4, numeral 20 indicates a pressure plate which can beopened and closed vertically. This pressure plate biases from above thesheet original D, document or the like arranged on the original glassstand 12, thereby bringing the reading image surface thereof into closecontact with the original glass stand 12.

Numeral 21 indicates a sheet original conveying portion, which movesvertically with the opening and closing of the pressure plate 20. Thesheet original conveying portion 21 separates a plurality of sheetoriginals S one by one from above, and conveys each sheet original to asheet original reading position B shown in FIG. 2.

The sheet original reading position B is defined by the flow readingglass sheet 13 and an original backup roller 21 i. The CIS 1 is moved tothe sheet original reading position B and stopped there, and then theimage of the original S conveyed by the sheet original conveying portion21 is read.

An original jump stand 4 serves as a partition between the flow readingglass sheet 13 and the original glass stand 12. The original jump stand4 constitutes a structure with a glass support portion 4 c serving assupport means (See FIG. 3) for clenching the original glass stand 12bilaterally from above and below.

The glass support portion 4 c also supports the lower surface of theflow reading glass sheet 13, downwardly regulating the position of theflow reading glass sheet 13. The thickness of the upstream-side endportion 4 d of the original jump stand 4 is set to be smaller than thethickness of the flow reading glass sheet 13, and the leading end of theoriginal is picked up by the original jump stand 4 to be conveyed towarddischarge rollers 21 j.

The portions of the jump stand 4 through which the height regulatingportions 2 pass have no glass support portion 4 c (to define recesses 4f), so that the image reading unit can smoothly reciprocate between theoriginal glass stand 12 and the flow reading glass sheet 13.

A protrusions 4 e on the lower surface of the jump stand 4, provided inthe region through which the height regulating portions 2 pass, isformed so as to be flush with or somewhat protruding beyond the glassback surface, whereby the height regulating portions 2 are preventedfrom colliding with the protrusions 4 e on the lower surface of the jumpstand 4 or the glass edge to thereby cause malfunction or damage.

Biasing springs 6 on the carriage 5 have a stroke not less than theprotrusion amount of the protrusions 4 e on the lower side of the jumpstand 4 of the guide portion, and their spring constant and free heightare set such that the upper portion of the CIS 1 protrudes beyond aposition of the bottom surface position of the original glass stand 12when the original glass stand 12 is removed.

Due to this arrangement, the CIS 1 is brought into contact with theglass back surface only by placing the original glass stand 12 fromabove, the CIS 1 is enabled to move smoothly, and it is possible toprevent the height regulating portions 2 from being worn. Further, apredetermined distance is maintained between the CIS 1 and the originalglass stand 12, whereby the focal position of the CIS 1 with respect tothe original is determined.

An original backup roller 21 i is raised with the upward opening of thepressure plate 20 so as to be separated from the flow reading glasssheet 13, making it possible for a jammed original to be cleared away inthis state.

When the pressure plate 20 comes down, the original backup roller 21 iis again brought into contact with the flow reading glass sheet 13 todefine the original reading position B.

In FIG. 1, when the CIS 1 is at the original flow reading position B,the width of the CIS 1 is smaller than the width of the flow readingglass sheet 13. Since the height regulating portions 2 are in contactwith the back surface of the flow reading glass sheet 13, cutouts 15 and16 are provided in some parts of the frame 3, thereby preventing theheight regulating portions 2 from colliding with the frame 3. Further,the central portion of the flow reading glass sheet 13 is supported by aframe 3 d.

When the original D kept at rest on the original glass stand 12 is readwhile moving the CIS 1 in the sub-scanning direction, the position Cconstitutes an extremity. At this extremity for the reading operation,there are also provided cutouts 17 and 18 in some parts of the frame 3,thereby preventing the height regulating portions 2 from colliding withthe frame 3.

Next, the operation of reading the original D at rest on the originalglass stand 12 will be described. When the pressure plate 20 is opened,it is detected by a pressure-plate opening/closing sensor (not shown),whereby the CIS 1 reads the back surface of a white reference plate 19provided at the end of the upper surface of the original glass stand 12to obtain white reference data for shading correction.

The white reference plate 19 is provided between the end 12 a of theoriginal glass stand 12 and the original-leading end position A (in FIG.2, the position A is the forward-end position in original reading), andthe home position of the CIS 1 is determined by a home position sensor(consisting of a photo interrupter) 23, thereby determining an obtainedwhite reference data value.

This apparatus allows reading of an original of up to the LDR size (432mm). However, since the enlargement and reduction is effected throughvariation in the sub-scanning speed, it is necessary to accelerate ordecelerate the stepping motor 11 when the scaling factor is small. Uponreceiving a signal instructing a reading of original, the CIS 1 startsto move in the sub-scanning direction from the white reference dataobtention position, and starts the reading of the original from theoriginal leading end position A.

When a large acceleration distance is required, the CIS 1 is temporarilybrought back to the end on the flow reading glass sheet 13 side (at thistime, the height regulating portions 2 are prevented from coming intocontact with the frame 3 due to the cutouts 15 and 16), and starts toaccelerate from there in the sub-scanning direction. The accelerationtable is prepared such that acceleration is completed before theoriginal leading end position A is reached.

At the moment that the CIS 1 passes the home position sensor 23, stepamount counting with respect to the CIS 1 is started, and image readingis started when the CIS 1, which has attained a fixed speed, reaches theoriginal leading end portion A.

After the reading of the original is completed, the CIS 1 is deceleratedbefore it stops. When the amount by which the decelerating CIS 1 isallowed to go beyond the end is large, it is usually necessary toenlarge the end portion of the original glass stand 12, resulting in anincrease in the apparatus size.

In the present invention, this is avoided by providing the frame 3 withcutouts 17 and 18 which allow the height regulating portions 2 to enterand stop therein. Thus, there is no need to enlarge the original glassstand 12. The end portion of the original glass stand 12 is supportedfrom below by the frame 3 e (support portion).

When the CIS 1 has stopped after deceleration, the stepping motor 11,serving as the driving means, rotates in the opposite direction, and theCIS 1 moves until it is detected by the home position sensor 23. Afterthe detection, the stepping motor 11 is stopped, and the CIS 1 remainson standby until the next image reading operation is performed.

Next, the operation of the CIS 1 in flow reading will be described. InFIG. 4, when a batch of originals is placed on the original tray 24, anoriginal detecting sensor 25 detects the originals, and the apparatusstarts an initial setting for flow reading operation. On the main bodysystem side, an indication is given through an indicating portion(display) 106 a on an operating portion 106 to indicate that theoriginal S is on standby, and key input operation is waited for.

When the original detecting sensor 25 is turned ON, it is determinedthat sheet originals S are on the original tray 24. However, when thepressure plate 20 is open by an angle larger than 15 degrees withrespect to the horizontal direction, a pressure plate opening/closingsensor (not shown) detects the open state of the pressure plate 20, andgives an indication to that effect through the indicating portion 106 a.When the user gives instructions for operation through key input, theoperation of the sheet original conveying portion 21 is restrained,thereby preventing defective conveyance of the originals.

Only when the original detecting sensor 25 is turned ON, and thepressure plate opening/closing detecting sensor (not shown) detects theclosed state of the pressure plate 20, flow reading operation at thereading position B is conducted. After the completion of the reading atthe reading position B, the CIS 1 is kept on standby at that positionfor a fixed period of time, responding to instructions for continuousflow reading operation. When no instructions are given for next readingoperation after the fixed period of time, the CIS 1 is returned to thehome position.

When a predetermined period of time has elapsed after the detection ofthe closed state of the pressure plate 20, or when operationalinstructions have been given by the user through key input, the mainbody system performs pre-scanning on the white reference plate 19 gluedto the upper surface of the original glass stand 12 by the CIS 1, andmoves the carriage 5, in which the CIS 1 is mounted, to the position B,which corresponds to the flow reading position. The distance by whichthe carriage is moved is counted in a predetermined number of stepsstored in a nonvolatile memory after the movement of the CIS 1 has beendetected by the home position sensor 23.

The reason for setting the flow reading position outside the region ofthe original glass stand 12 is as follows. In the original conveyingportion on the pressure plate 20 side, corresponding to the flow readingposition, there are provided mechanism parts such as rollers and anopening for allowing sheet passage. If the flow reading position is onthe original glass stand 12 side, the shadow of the opening will be readwhen an original of a size smaller than the recording size of theoriginal glass stand 12 is read, with the result that the shadow of theopening of the sheet scanner portion is allowed to be recorded in a parton either side of the recorded image, resulting in a deterioration inthe image quality.

When the detent torque of the stepping motor 11 is large, or when thegear ratio is large, a large braking force is applied due to the momentof inertia of the CIS 1 and the biasing force applied to the originalglass stand 12, so that it is possible to set the CIS 1 at rest, withoutsupplying a stop energization current to the stepping motor 11.

In this case, motor control is released, so that it is only necessaryfor the system to control the sheet scanner motor 21 r (FIG. 6). Thatis, operation is possible by switching between the motors controlled bya single control circuit, so that the cost involved is lower as comparedwith the case in which two control circuits are provided.

Next, an example of a construction in which this image reading apparatusis mounted in a copying machine will be described. This copying machineis provided with a flat bed scanner which reads an original image bysetting the original on the original glass stand 12 and moving the CIS1, and a (flow reading) sheet scanner which reads an original imagewhile conveying the original so as to bring it into contact with theflow reading glass sheet 13 arranged at substantially the same height asthe original glass stand 12, instead of scanning an original conveyed toand set at rest at a predetermined position as in the case ofconventional copying machines.

As shown in FIG. 5, a recording sheet discharging portion 101 isprovided below the reading portion 103. Below the recording sheetdischarging portion 101, there is provided a recording portion 102(laser beam printer) which is equipped with image forming means forforming a toner image on a recording sheet consisting of paper or thelike in accordance with an image signal obtained by the reading portion103, etc. The recording portion 102 is provided with atoner-integral-type process cartridge 107.

At the front of the recording portion 102, there is provided amulti-feed portion 104 capable of feeding recording sheets of varioussizes, and, in the lowermost portion, there are provided front loadingcassettes 105 which can be drawn out to the front. The cassettes 105 canbe provided in a plurality of stages, each cassette 105 consisting of auniversal cassette allowing changes in the sizes of the recording sheetsused.

The operating portion 106 and the reading portion 103, which are mostfrequently used by the user, are arranged at positions that are mostconvenient for operation, and the recording sheet discharging portion101, whose frequency of use is next to that of the above-mentionedcomponents, is provided below them. The toner-integral-type processcartridge 107 is arranged below the recording sheet discharging portion.Since the large-capacity cassettes 105 are arranged in the lowermostportion, the number of times that recording sheets are supplied isreduced to thereby reduce the number of times that operation isperformed, and it is possible to minimize the installation space for thecassettes 105.

In this way, the operating portion 106, the original reading portion103, the recording sheet discharging portion 101, the process cartridge107, and the cassettes 105 are arranged from above in the order offrequency of use, thereby facilitating the operation to improve theoperability.

The recording sheet discharging portion 101 is provided in the spacebetween the recording portion 102 and the reading portion 103, therecording sheets being discharged from the back toward the front as seenby the user.

Due to this arrangement, an improvement is achieved in terms ofvisibility of the recording sheets as compared with the conventionallateral discharging. Since the paper feed portion 104 does not stickout, the space for installation is reduced, and the user is enabled toextract recording sheets while standing, whereby an improvement inoperability, etc. is achieved.

Further, a part of the sheet discharging portion 101 constitutes acartridge cover 102 a for the toner-integral-type process cartridge 107,and the cartridge cover 102 a can be opened within the space of thesheet discharging portion 101. Further, taking account of theoperability of the process cartridge 107, a cartridge guide is providedin the apparatus main body such that the process cartridge can be drawnout to the front obliquely upwards.

Further, at the back of the space of the sheet discharging portion 101,there is provided a jam removal cover 101 a. By opening this jam removalcover 101 a to the front, the pressure of the recording sheet conveyingdrive system is released, and the jammed recording sheet can be drawnout to the front. In FIG. 5, numeral 102 c indicates a laser opticalunit for image generation, numeral 102 d indicates an image transferportion, and numeral 102 e indicates a fixing portion.

As described above, in this embodiment, the cutouts 15, 16, 17, 18 areprovided in some parts of the frame 3 at the ends of the image readingregion, and the height regulating portions 2 are prevented fromcolliding with the frame 3 which serves as the support portion forsupporting the glass sheets 12, 13. Thus, the apparatus size can bereduced as compared with the case in which the support portions of theframe 3 supporting the end portions of the glass sheets 12, 13 areprovided outside the movement region for the CIS 1. Further, since nocutout is provided between the cutouts 15, 16 or between the cutouts 17,18, it is possible to support in a stable manner an original glass standwhich is relatively heavy. Thus, it is possible to prevent generation ofdistortion due to insufficient support for the original glass stand bythe frames, with the result that it is possible to prevent defectivereading of images by the CIS 1.

FIG. 7 shows another embodiment of the present invention. As shown inFIG. 7, the sheet original S is read as it is moved. When, in this case,the sheet is conveyed toward the exterior of the apparatus from theoriginal glass stand 12, there is no need to provide the jump stand 4between the flow reading glass sheet 13 and the original glass stand 12,so that the two glass sheets can be integrated.

In this case, as in the above-described embodiment, there are providedthe cutouts 15, 16, 17, and 18 for preventing abutment against the frame3 of the height regulating portions 2 of the image reading unit (i.e.,the height regulating portions 2 for regulating the height of the CIS 1)in the glass support portion on the right-hand end portion of theoriginal glass stand 12.

On the other hand, due to the absence of the jump stand 4, the left-handend portion of the original glass stand 12 is supported by the frame 3.However, it is also possible, as in the case of the flow reading glasssheet 13, to provide the cutout 15 as the escape means for the heightregulating portions 2 to support the original glass stand 12.

As described above, when adopting a CIS of a shallow focal depth as theimage reading means, the support means is provided with cutouts forpreventing the image reading unit from abutting against the supportmeans when the image reading unit moves outwardly beyond the end of theoriginal resting means, whereby it is possible to move the image readingunit up to the end portion of the original resting means.

Thus, as compared with an image reading apparatus and an image formingapparatus in which the original resting means is supported by supportmeans at positions corresponding to areas outside the movement region ofthe image reading unit, a reduction in apparatus size can be achieved.

1. An image reading apparatus comprising: a transparent plate forsupporting an original thereon; a support member for supporting an endportion of the transparent plate at a surface of the transparent plateopposite to the original; and a movable image reading unit for readingimage information of the original, the image reading unit including animage sensor for reading image information of the original and aregulating member for regulating a distance between the image sensor andthe transparent plate, wherein the regulating member slides on thesurface of the transparent plate opposite to the original when the imagereading unit moves, wherein the support member is provided with a cutoutin a moving direction of said movable image reading unit so theregulating member slides with respect to the transparent plate when theimage reading unit moves to the end portion of the transparent plate. 2.An image reading apparatus according to claim 1, wherein the regulatingmember is provided outside a readable region of the image sensor in adirection perpendicular to a moving direction of the image reading unit.3. An image reading apparatus according to claim 1, wherein thetransparent plate is provided with a glass sheet on which the originalis to be rested, and wherein the support member supports an end portionof the glass sheet.
 4. An image forming apparatus comprising: atransparent plate for supporting an original thereon; a support memberfor supporting an end portion of the transparent plate at a surface ofthe transparent plate opposite to the original; a movable image readingunit for reading image information of the original, the image readingunit including an image sensor for reading image information of theoriginal and a regulating member for regulating a distance between theimage sensor and the transparent plate, wherein the regulating memberslides on the surface of the transparent plate opposite to the originalwhen the image reading unit moves; and a recording portion, wherein thesupport member is provided with a cutout in a moving direction of saidmovable image reading unit so the regulating member slides with respectto the transparent plate when the image reading unit moves to the endportion of the transparent plate.
 5. An image forming apparatusaccording to claim 4, wherein the regulating member is provided outsidea readable region of the image sensor in a direction perpendicular to amoving direction of the image reading unit.
 6. An image formingapparatus according to claim 4, wherein the transparent plate isprovided with a glass sheet on which the original is to be rested, andwherein the support member supports an end portion of the glass sheet.7. An image reading apparatus according to claim 1, wherein thetransparent plate is a flow reading glass sheet, and the image sensorreads image information of the original while the original is moved incontact with the transparent plate.
 8. An image forming apparatusaccording to claim 4, wherein the transparent plate is a flow readingglass sheet, and the image sensor reads image information of theoriginal while the original is moved in contact with the transparentplate.